phase is collected or discarded, depending on whether it contains the desired analytes or undesired impurities. If the portion retained on the stationary phase includes the desired analytes, they can then be removed from the stationary phase for collection in an additional step, in which the stationary phase is rinsed with an appropriate eluent.

It is possible to have an incomplete recovery of the analytes by SPE caused by incomplete extraction or elution. In the case of an incomplete extraction, the analytes